600MW汽轮发电机转子绕组接地故障及匝间短路分析与诊断

Analysis and Diagnosis of Ground Fault and Inter-turn Short Circuit of Rotor Winding in 600MW Turbo-generator

本文介绍一台600MW汽轮发电机转子绕组接地故障查找方法。当汽轮发电机转子绕组发生接地故障时,可用大电流法进行试验,计算大致接地距离。对于转子绕组为氢内冷的汽轮发电机,要准确查找轴向和周向的接地位置,不必在转子轴上通大电流,可在绕组两极施加直流电压,借助通风孔测量对地电位进行查找。该机由于金属异物造成极间短路,进而发展为转子绕组接地,造成护环损坏的严重后果。当发生类似极间短路的严重短路故障时,由于短路电流较大,易烧损转子部件,严重时还会出现接地故障。当确定转子绕组同时发生了匝间短路和接地故障时,发电机应立即停机。因此,应研究转子绕组同时发生匝间短路和接地故障时转子一点接地保护作用于跳闸的可能性,以防止事故扩大。

This paper introduces a kind of rotor winding grounding fault locating method. When the rotor winding of turbo-generator has grounding fault, a large current method can be used for diagnosis and it can find the grounding position roughly. But the large current method need a large capacity power supply and has the risk of damaging rotor. For hydrogen-cooled rotor of turbo-generator, to locate the axial and circumferential earthing position, a method that applied DC voltage on rotor winding poles and measured the ground potential by vent hole can be used instead of large current method. The magnetic pole-to-pole short-circuit of rotor winding was caused by foreign metal bodies in a power plant 600 MW turbo-generator, then developed the grounding fault,caused serious damage on retaining rings of generator rotor. When severe short-circuit fault as magnetic pole-to-pole short-circuit occurred, the rotor parts was easy to burn because of the large short circuit current, even caused the grounding faults. When both inter-turn short circuit and grounding fault happened simultaneously,the generator should be stopped immediately. Therefore,in order to prevent the accident, the possibility of the rotor one point grounding fault protection acting on the trip should be researched when both rotor windings inter-turn short circuit and grounding fault happened simultaneously.